Method of cleaning quartz sand to remove various impurities, in particular iron compounds with a aqueous liquid acid solution

摘要

1454577 Purifying quartz sand A AHLSTROM OSAKEYHTIO 26 June 1974 [5 July 1973] 28366/74 Heading C1A In a process for purifying quartz sand by reacting it with aqueous HF (e.g. 2-30 wt. per cent) at elevated temperature (e.g. at 70- 80‹ C. for maximum 30 mins.), HF is regenerated from a separated liquid phase containing silicofluoric acid by reacting it with NH 3 or a solution thereof (e.g. at 70-80‹ C.), thereby precipitating silicic acid, adding H 2 SO 4 to precipitate (NH 4 ) 2 SO 4 and recovering a solution containing free HF, which may be recycled. The sand may first be washed with water or acid to remove lone impurities, or subjected to magnetic separation of iron.